1. Field of the Invention
This invention relates generally to oxidizing formaldehyde. It relates particularly to a process for oxidizing formaldehyde to carbon dioxide and water, which process includes exposing a gaseous mixture containing formaldehyde and an oxidizing agent to a catalyst of a noble metal dispersed on a metal oxide possessing more than one stable oxidation state.
2. Description of the Related Art
In many applications it is highly desirable, if not necessary, to remove formaldehyde from the medium in which it exists as an unwanted, toxic impurity. By way of example, there has been a long-standing need for a method to remove formaldehyde from indoor air--i.e., breathable air in enclosed spaces such as homes, automobiles, airplanes, hospitals, or industrial plants where the air contains undesirably high concentrations of the toxic formaldehyde. Other significant long-standing needs include the need to remove formaldehyde from compressed air and other oxygen-containing gases, as well as the employment of personal safety masks in the removal of high concentrations of toxic formaldehyde from the ambient atmosphere.
Prior methods employed to remove formaldehyde in such applications include filtering and exhausting to outside air. These methods have been shown to be unsatisfactory for the following reasons: (1) Filters employ a surface on which the species to be removed is adsorbed. The amount of the species to be removed depends on the total number of active surface sites available for adsorption. Once all sites are occupied, the filter ceases to work and must be replaced. (2) Filters in use contain the toxic formaldehyde in adsorbed form and must be disposed of as toxic waste or incinerated. (3) Exhausting to the outside air requires extra duct work and is a source of pollutant formaldehyde to the atmosphere.
It is accordingly a primary object of the present invention to provide an efficient means for removal of formaldehyde from the medium in which it exists as an unwanted, toxic impurity, without the use of filters and further without the addition of energy (e.g., heat).
It is another primary object of the present invention to provide for the removal of formaldehyde from the medium in which it exists as an unwanted, toxic impurity, by presenting a catalytic process for the oxidation of formaldehyde to carbon dioxide and water without the addition of energy (e.g., heat).